S14 is based on M10 block as I said before... M42 is based on the same block as M40 M44 M43 so be sure that S14 head won't fit M42 block... It is longer, wider and completely different.
And it would not do any better to have swapped the S14 head... Of corse flow is much higher with S14 head, but it is completely different engine - made to rev much higher and it also has much bigger displacement /i mean 2,3 and 2,5 ltr/
You have to ask Yourself what You really want to achieve, before trying to fit S14 head into the M42...
If You want better flow, just dig the channels, the potential is really simillar/when You recalculate displacement/, but I must admit here that M42 is much more sophisticated engine made very well in stock. Try to dig channels, change into individual throttle bodies or bore it and You have to change the data in the ECU, and You should change AFR because it will limit the flow. And more -> You can forget about low consumption or nice low end torque...
It is much easier to swap whole S14 driveline... Especially when You are afraid of "much work".
I would rather change this iritating heavy flywheel and add air filter with better flow, put there a chip and be sure You full the tank with proper octane gasoline... You can easily change to 4,27 LSD and finally You've got it - perfect handling sport car... capable of 190km/h with hell much fun from driving it :-) And still very economic compared to other that strong cars.
On the other hand -> I am just mad about M42 turbo capable of 9000rpm and far above 400HP's.... It is surely possible, but where the hell would I drive it?
After phoning ALL the track's here in the area - We've got no chance at all to race our little beauties on open track days like in the US...
